Radio signaling system



Nov. 11, 1930. A. BAsLEY RADIO SIGNALING SYSTEM Filed Dec. '7, 1927 INVENToR. @u z/m@ ATTORNEY rana@ new. ii, ieee AUSTIN BAILEY, F MAPLEWOOD, NEWA JERSEY, ASSIGNOR TO AMERICAN TELEPHONE .AND -TELEGRAPH COMPANY, A.- CORPQRATION 0F NEW 'YORK I RADIO SIGNALING SYSTEM Application died Eecember 7,' 1927. Serial No. 238,377.

This invention relates to radio transmission systems and particularly toarrangements in such systems for combining'the outputs of two or more circuits.

In radio receiving systems in which it is necessary t'o maintain a high degree of selectivity in reception,- highly directive antenna systems are particularly desirable.- yDirective antenna systems are usually obtained by equally well for combining two or more out-'- put circuits derived from a single antenna.

One form of antenna which has been found to be highly successful Iin practice is known in .the art as the wave antenna. .While this invention'will be .disclosed with particular reference -to its use in connection with a wave antenna or an array of waveantennae,V

itwill be apparent that it is applicable to any antenna array. p

In an ordinary use of wave antennae, as is well known in the art, a small fraction of the interference or noise voltages developed in the surge resistance of a wave antenna may be used to balance out undesired interference and noise received by the antenna from a direction-'different from that of the desired signal. This process of neutralization is termed compensation and may serve in efect to produce zero o r negligible receptionyat any desired an le, i. e., at any angle dierent from the ang e of the desired signal.

The directivity of a receiving .system may be increased by the use of parallel wave antennae spaced apart a certain fraction 0fawave length in a direction at right angles to that of the desired signal, eachwaveantenna, however, being substantially parallel to the line offtravel of the desired signal. Such an arrangement is 'often referred to as a `,broadside wave antenna system and its effect, in general, is to increase the direc- -tivity or-rather the discrimination against signals or noise coming from other than the desired direction. In such a system, compensation may also be employed to redu:e the ,reception of interference or noise to` aconsiderable extent. I

I n'accordance with the present invention, it is proposed to bring to a common point not only the desired signals impressed upon two or more wave antennae but also voltages representing undesired signals lor interferences which may be set up in antennae by waves or disturbances in space. The signals vwhich may be brought lto the common oint from the wave antennae maybe com ined y under suitable conditions of phase and amplitude and similarly the voltages represent# ing undesired signals or interferences may also be combined under similar conditions of phase and amplitude. The latter voltages may then be utilized to balance out noise and interference coincident with the desired signals in the terminal circuit of the said wave antennae. In order to accomplish the object of this invention, means maybe provided for combining the outputsof the wave antennae so that there will bea somewhatadditive effect for `the desired signals in the output ofthe vcombining means andso that there may be zero or negligible interaction between the input circuits of the combining means. In other words, it is intended to provide. means whereby the currents iowing in the input circuits may be mutually independent and non-4 react-ive and still these currents may'become suitably combined by the combining means. One form of combining means which will be described hereinafter comprises a number of impedance elements, interconnecting an output circuit which may lead to a radio receiver andl two input. circuits over which the currents to be combined may flow. In the particular form of combining" network to be de scribed hereinafter, the impedance of each of these elements is preferably equal to the A 'of the wave antenn cannot become impressed upon the other of the .input circuits similarly connected .to one or more 'of the' wavelantennae, and-vice versa. Also,vif the desired signals impressed upon the respective input circuits are brought into phase equality, the output or receiving circuit may rederstood from thedetailed description here-y inafter following, when read in connection with the accompanying drawing in which Figure 1 shows one form of receiving system to which this invention has been applied, the

system comprising two antennae connected in broadside, Fig. 2 represents a network` composed of elements of resistance forming a combining circuit, and Fig. 3 represents a network composed of elements of reactance as well as of resistance'to formacombiningV circuit. y Referring' to Fig. l of the drawing, two wave antennae A andfB are shown, each consisting of two or more parallel wires extending across the country substantially parF allel to the direction of travel of the signals to 'be received. It is to be distinctly understood, however, that the principles of this invention may be applied to any number of wave antennae or other antennae constituting an array. VAssuming that each antenna' eX- tends, for example, from east to-west, then a.

signal whichc'omes from the east gradually `builds up by increments, reaching its maximum value at the west end of the antenna. In other words, the current in the antenna will gradually grow in amplitude as the signaling wave travels along its surface. `Yet, if it is desired to receive the signaling wave which approaches the antenna from'the east-4 ern direction, the amplitudel of the current set up by the signaling wave at' the eastern terminal ofthe antenna will be extremely small, if not negligible. While, at the western ter- `minal, the amplitude of the current will be considerably larger and a maximum.

It may sometimes be necessary to locate the receiving apparatus near the eastern terminal of the'antenna. In order to permit such a location, the antenna is terminated at the western terminal in a reflection 'transformer such as RT1 so that the antenna conductors serve not only to pick up the waves 4in space but: also maybe employed as e., transmission line for transmitting fromI the western terminal tothe eastern terminal, the currents resulting from the voltages built up in the antennae. The midpoint of the secondvary winding of the reection transformer RT1 is connected through the primary winding of that transformer toy ground'. By.

means of these connections, the-current Hows to ground through the primary winding of the reflection transformer RT1 and the voltage created thereby across thewinding bridging the conductors of theiantenna A causes the vflow of current over the conductors as a metallic circuit. At the eastern terminal of the antenna another transformer vST1 is 1o- 'cated', the midpoint of the primary winding of which is connected to ground through the primary winding of another transformer CT1 which isso constructed that with its attached circuits, itl serves to lproperlyterm'inate the antenna. The resistance thus interposed between the eastern terminal of the antenna A and ground is often spoken-of as the surge resistance. The transformer ST1 associatesthe metallic circuit of the antenna A with a transmission line A1, this line leading to a receiver by way of apparatus to be subsequently described.- The voltage'resulting from an undesired signal buildsfup' in each conductor of antenna A in the opposite direction, i. e., from west lto east along the antenna and substantially equal currents resulting therefrom' will iow vthrough the halves of the primary winding of transform' .er ST1: oppositely to ground by virtue of the connection to ground of the mid ointof the primary winding of transformer T1) ythence through the primary winding of the transformer CTI. No effects will beproduced in the secondary Winding of the transformer ST1 and accordingly the local line Al will be-substantially unaffected by such currents.

A wave antenna of the type described eX- hibits considerable directional selectively, receiving signals flowing from eastto West with high eciency. Since this wave antenna is y not purely unidirectional in its characteristic as discussed hereinabove, signals approaching at angles substantially different from the angle of desired signals may also be received.

While the energy level of such signalslmay be relatively low, the level may be 'sucien however, to cause the introduction ofnoise and interference into the receiving circuits. The amount of noise orinterference introduced by signals different Ifrom the desired signals will depend upon the direction from which they are coming. Signals coming, for example, from the north and from the south i. e., perpendicularly to. the antenn, will hardlyv be received, if 'at all. Yet, it maybe important to compensate or balance out the noise or interference 'derived from signals coming from still other directions.

So far, the apparatus has been described with respect to a single wave antenna. When a plurality of' antennae are are employed (only two of which are shown herein for -illustrativepurposes) each may be provided lie with equipment similar to that described in l connection with antenna A. A signal moving in the direction from east to west impressed upon the antenna B will be trans- 1,7so,eea

mitted to reflection transformer R'll2 and back over the conductors of the" antenna to a local circuit B1. The current of undesired signals picked up by antenna B willbe suby stantially non-effective in the local circuit, B1

antennae A arid B flowing in the local circuits A1 and B1 may be combined in a common circuit C1 by means Aof a network S1, the details of certain forms of which are shown in Figs.v

2 and 3 of the drawing. It is, of course, necessary for a suitable combination of these signaling components that they he impressed upon the network S1 in phase with each other. It may also be necessary, in practice, that the signaling'components from the antennaeA and Bbe impressed upon the network S1 at the same or substantially the same amplitudes. These .results may ordinarily be obtained by making circuits A1 and B1 of substantially equal length. Yet, if the geographical situation is such that these lines may not be of substantially equal length, they may be made o the same length by providing indirect routes between the network S1 and the eastern terminals of the antenn. As an. alternative, the shorter line may be made electrically of the same length as the longer line by interposing'in the shorter line an artificial line section which may consists of a phase shifter P1 and an attenuator L1, introducing phase shift* and loss equivalent to the difference between these lines.

In a similar manner, the noise or interference currents flowing through the"primary windings of transformers ST1 and CT2'related to the antennae A and B, respectively, may be transmitted to another network S2 over lines A2 and B2,respectively, and there arranged for suitable combination in a circuit C2. It will be understood that the network S2 may be of the same general type as network S1, which will be more fully described hereinalter. Here, again, it may be necessary that the components taken from the respective antenn be impressed upon the network S2 in the same phase with each other and atequal amplitudes. The lines A2 and B2 may be of substantially equal length or maybe electrically of substantially equal length as described hereinabove. 'A phase shifter P2 and an attenuator L2, both of which are well known in the art, may be included in one of the lines such as B2. bviously, the phase shifter P2 serves the purpose of adjust ing the phase of a compensating current comn ing through transformer GT2 to equal the phase of the compensating current coming through transformer ST1, phase equality being necessary te a suitable additive combination of the respective currents. Similarly, the attenuation adjuster or attenuator L2 may, if desired, be Varied so that the current flowing in the local circuits B2 is substantially equal in magnitude to the current flowing in the local circuit A2.

The networks S1 and S2 are connected to networks N1 and N2, respectively. Networks N1 and N2 preferably comprise elements of resistance, as will be described in connection with Fig. 2, or elements of resistance and reactance, as will be described in connection with Fig. 3. The networks N1 and N2 may terminate the networks S1 and S2 in impedances substantially equal to the impedances looking into the lines C1 and C2 from the networks S1 and S2, respectively.

As described hereinabove, the signaling currents are combined in the common circuit C1 together with such noise and interference currents resulting from undesired signals or disturbances as may be picked up by the wave antennae Av and B. The compensating noise and interference currents brought together by circuits A2 and B2 are combinedin a common circuit C2. In order to free the signaling currents ,from the noise and the interference currents superimposed thereon, the compensating noise currents from the circuit C2 may be impressed on the circuit RC together \with all currents from the circuit C1 through the medium of the network Ss which is preferably of the same general type as networks S1 and S2. It may be, of course, necessary that the compensating current and noise or, interference current to be compensated shall be of substantially equal amplitudes and 180 degrees out of phase. Accordingly, a phase shifter P3 and an attenuation adjuster L3 are interposed between the network S1 and the networks S1 and S2, respectively. The phase shifter may be manipulated to bring about a 180 degree phase variation necessary to properly combine the current in the circuit C1 to be compensated with/the compensating current in the circuit C2 for effective neutralization. The attenuation adjuster L3 may serve to render the magnitude of the compen sating current in the circuit C2 the same as that ot the current to be compensated in the circuit C1, this being a condition which also must be uliilled for effecting neutralization 1 of these combining currents. A network N3 which may be similar in character to the networks N1 and N2`is connected to the network S3, network N3 having an impedance substantially equal to the impedance of the circuit RC. After the adjustments above mentioned shall have been made for the phase and magnitude of the compensating currents as well as for the currents to be compensated, the receiving circuit` RC will receive the desired signals substantially free from the e'ects of the noise or interfering currents.

ln using the system, ci this invention, the

iis

varied conditions brought about by the im-l n pression of signals from various angles on the wave antennae, it may be necessary, at intervals, to readjust the phase shifters and attenuators representing the compensating apparatus, in order to preserve the required degree of balance against these waves.

In Fig. 2 of the drawing, there is shown a network arrangement for combining the currents flowing in two separate circuits. Thev form of arrangement represented in this ,figure comprises a number of resistances, each of which may be equal in magintude to the resistance of the output or receiving circuit RC. 2 Une input circuit such as D1 may be connected to terminals a and b, while another input circuit may be connected to terminals c and d, terminals a, I), c and al constituting the terminals of an arrangement such as` anyone ofthe networks S1', S2 and S2 of Fig. 1 may be. A' resistance unit Rl may comprise a network which may'fulfill the requirements of anyone of the networks N1, N2 and N 2 of Fig. 1. Resistance R1 is connected between terminals a and c. Resistances R2 and R3 are connected between terminals a and d and terminals b and c, respectively. Each of the resistances Ri, R2 and R3 may preferably be of a magnitude corresponding to the magnitude of resistance in the output of receiving circuit RC.

It will be apparent that resistances R1, R2 and 3 compose three of the arms of a Wheatstone bridge arrangement, the .fourth arm of which is the output or receiving circuit RC. The input circuit D1 is connected to one of the diagonals of the bridge, the terminals of which are formed by resistances R1 and R2 and resistance R2 and the output or receiving circuit RC, respectively. The other input circuit D2 is connected tothe other of the diagonals of the bridge, the terminals of which are formed by resistances R1 and Ra and the resistance R2 and the output or receiving circuit RC, respectively. Since the elements R1, R2 and R3 may be designed to have magnitudes of resistance equal to the resistance of the output or receiving circuit RC, the bridge will be balanced and the current flowing in one of the` input circuits will cause no potential drop in the other of the input circuits, and vice versa. Consequently, the currents fiowing in these input circuits will be mutually independent and nonreactive. The output or receiving circuit RC will receive the energy of these input circuits,

here also, an arrangement similar to the one described in connection with Fig. 2 of the drawing. In this Wheatstone bridge, arrangement, however, each of the arms of the bridge may be composedof adjustable elements of inductance, capacitance and resist-l ance. Three of the arms of the bridge may include adjustable resistances Ru, R12 and R12,

variable condensers K1, K2 and, K2 and three windings L1, L2 and L3 adjustable 1n lnductance values, respectivel The fourth arm of the bridge is formed y the output or receiving circuit RC. As in Fig. 2 of the drawing, the input circuits D1 and D2 are connected to the diagonals of the bridge.

The three arms of the bridge of which the output or receiving circuit RC is the fourth arm may be adjusted to have components of j resistance, capacitance and inductance each f equal to the corresponding compounds in the output ory receiving circuit RC. -When such an adjustment iseifected, the bridge arrangement becomes balanced s'o that the input circuits D1 and `D2 are mutually independent and non-reactive, i. e.,-the How of current through one of these circuits causes no flow of current4 in the other of these circuits and Vice versa. The output or receiving circuit RC receives all of the energy in the input circuits Dr and D2 minus the energy dissipated in the resistance elements of the other arms of the bridge.

While this invention has been disclosed in connection with two wave antennae, it will be appa-rent that it is applicable to any number of antennae. Thus, side antenna syst-em employing three antennae were used, the outermost antennae could be connected with a network or networks for the combination of their signaling currents in the manner shown in Fig. l.

ySuch combined currents could then be applied to another network or networks togetherwith the signaling current from ,the middle antenna to produce a resultant representingthe combination of all said currents. In like manner, the compensating currents from the three antennaecould be combined by bringing together the. interference from the for example, if a broadouter antennae and combining the resultant with interference from the inner antenna. rl`hese compensating currents could then be combined with the resultant signaling currents (upon which noise or interference may be superposed) so as to effectively neutralize such noise or interference. It is desirable to point out that the transpositions in the transmission lines A1 and 5 A2 connected with the antenna A (see Fig. l) are for the purpose of preventing crosstalk or other interference between these currents owing over these lines.

While this invention has been pointed out in certain particular embodiments merely for the purpose of illustration, it will be clearly understood that the general principles of this invention may be applied to other and Widel ly varied organizations Without departing from the spirit of the invention or the scope of the appended claims,

'What is claimed is: 1. The combination with a broadside antenna system of a combining circuit having a resistance netv ork to combine radio frequency currents representing signals and intei-ference superposed thereon, a resistance network to combine radio frequencyinterference currents, and a resistance network to oppose the currents of said first resistance network against those of said second resistance network to eliminate the e'ect of said interference in a receiving circuit.-

2. The combination with a broadside antenna system of a combining circuit having means to combine radio frequency currents representing signals and interference superposed thereon, means to combine radio frequency interference currents, and means including a conjugate network to oppose the currents of said first combining means against those of said second combining means to eliminate the edect of said interference in a receiving circuit.

In testimony whereof, I have signed my name to this specification this 5th day of December, 1927.

AUSTIN BAILEY. 

